Make "is" and "prefix" optional in "create an element"

dom.bs

@@ -3742,9 +3742,9 @@ dom-Range-extractContents, dom-Range-cloneContents -->
   <p>If <var>node</var> is an <a for=/>element</a>, then:
 
   <ol>
-   <li><p>Let <var>copy</var> be the result of <a>creating an element</a>, given <var>document</var>,
-   <var>node</var>'s <a for=Element>local name</a>, <var>node</var>'s
-   <a for=Element>namespace prefix</a>, <var>node</var>'s <a for=Element>namespace</a>, and the
+   <li><p>Let <var>copy</var> be the result of <a>creating an element</a>, given
+   <var>document</var>, <var>node</var>'s <a for=Element>local name</a>, <var>node</var>'s
+   <a for=Element>namespace</a>, <var>node</var>'s <a for=Element>namespace prefix</a>, and the
    value of <var>node</var>'s <code>is</code> attribute if present (or null if not). The
    <var>synchronous custom elements flag</var> should be unset.
 
@@ -4709,8 +4709,8 @@ invoked, must run these steps:
  "<code>application/xhtml+xml</code>", and null otherwise.
 
  <li>Let <var>element</var> be the result of <a>creating an element</a> given the
- <a>context object</a>, <var>localName</var>, null, <var>namespace</var>, <var>is</var>, and
- with the <var>synchronous custom elements</var> flag set. Rethrow any exceptions.
+ <a>context object</a>, <var>localName</var>, <var>namespace</var>, null, <var>is</var>, and with
+ the <var>synchronous custom elements</var> flag set. Rethrow any exceptions.
 
  <li>If <var>is</var> is non-null, then <a>set an attribute value</a> for <var>element</var> using
  "<code>is</code>" and <var>is</var>.
@@ -4737,7 +4737,7 @@ invoked, must run these steps:
  {{NotFoundError}}.
 
  <li><p>Let <var>element</var> be the result of <a>creating an element</a> given
- <var>document</var>, <var>localName</var>, <var>prefix</var>, <var>namespace</var>, <var>is</var>,
+ <var>document</var>, <var>localName</var>, <var>namespace</var>, <var>prefix</var>, <var>is</var>,
  and with the <var>synchronous custom elements</var> flag set. Rethrow any exceptions.
 
  <li>If <var>is</var> is non-null, then <a>set an attribute value</a> for <var>element</var> using
@@ -5444,10 +5444,14 @@ required to do so. The standard has this concept for readability.
 
 <p>To
 <dfn export id=concept-create-element lt="create an element|creating an element">create an element</dfn>,
-given a <var>document</var>, <var>localName</var>, <var>prefix</var>, <var>namespace</var>,
-<var>is</var>, and optional <var>synchronous custom elements flag</var>, run these steps:
+given a <var>document</var>, <var>localName</var>, <var>namespace</var>, and optional
+<var>prefix</var>, <var>is</var>, and <var>synchronous custom elements flag</var>, run these steps:
 
 <ol>
+ <li><p>If <var>prefix</var> was not given, let <var>prefix</var> be null.
+
+ <li><p>If <var>is</var> was not given, let <var>is</var> be null.
+
  <li><p>Let <var>result</var> be null.
 
  <li><p>Let <var>definition</var> be the result of